IP telephony gateway - solution for telecom switches

ABSTRACT

The present invention discloses a network control device (CPS) for controlling data transfer in a first network (IP), wherein the data transfer is supplied from a second network (SCN) via a switch device (SD) adapted to control the second network (SCN) and an interface establishing device (GW) connected between the switch device (SD) and the first network (IP), and said network control device (CPS) controls the interface establishing device (GW) by using signalling associated with the first network (IP). By applying the network control device according to the invention, a gateway between the first and the second network can easily be installed.

FIELD OF THE INVENTION

[0001] The present invention relates to a network control device and aninterface establishing means.

BACKGROUND OF THE INVENTION

[0002] In the following, some network elements important for thebackground of the invention are described by referring to FIG. 1.

[0003] In FIG. 1, two different networks are shown, an IP based networkand a circuit switched network SCN like a public switched telephonenetwork (PSTN) or a GSM network. These networks are connected bygateways GW1 and GW2, which are connected to switch devices SD1 and SD2,respectively. The switch devices SD1, SD2 and SD3 are conventionalswitches and serve to operate the SCN network. In detail, exchangeterminals for a trunk line are connected to the switch devices. It is tobe noted that for simplifying the illustration only an exchange terminalET connected to the switch device SD3 is shown. Nevertheless, also theother switch devices SD1 and SD2 comprise exchange terminals.

[0004] Furthermore, an important network element for the IP network is aso-called gatekeeper. In FIG. 1, a gatekeeper GK connected to the IPnetwork is shown as an example. In general, a gatekeeper is an elementin a network, that is responsible for registration, admission and status(RAS) of terminals and gateways. The gatekeeper participates in zonemanagement, call processing and call signalling according to the ITU-Trecommendation H.323 and provides address translation. Thus, thegatekeeper determines the route for signalling and media transport (datatransport) of call through the network. In this respect, the gatekeeperknows and controls the state of the IP telephony calls in an analogousway to a normal telecom switch (e.g., the switch device SD3) for aswitched circuit network (SCN), like GSM or a normal PSTN. Thegatekeeper GK normally handles IP telephony calls by using IPsignalling, for example H.323 signalling or other relevant IPsignallings like SIP (Session Initiation Protocol).

[0005] To the IP network a terminal TE is connected, which can be acomputer with a telephone connected thereto, for example.

[0006] In the following, the gateways GW1 and GW2 connected to theswitch devices SD1 and SD2, respectively, are described in more detail.A gateway provides an interface between two different networks, in thepresent case, between the SCN network and the IP network. Usually, agateway is composed of a signalling gateway, a media gateway and a mediagateway controller.

[0007] The signalling gateway provides the signalling mediation functionbetween the IP domain and the SCN domain. It may support functional orsignalling mediation between the IP domain (e.g., H.323) and callsignalling in the SCN domain (e.g., channel associated signalling ornon-channel associated signalling).

[0008] The media gateway provides media mapping and/or transcodingfunctions. It maps (e.g., tandemfree operation) or transcodes the mediain the IP domain (media transported over IP) and the media in the SCNdomain (e.g., PCM encoded voice, GSM, etc.).

[0009] The media gateway controller is located between the mediagateway, the signalling gateway and the gatekeeper. It provides the callprocessing (call handling) function for the gateway. It controls themedia gateways, it receives SCN signalling information from thesignalling gateway and IP signalling from the gatekeeper.

[0010] Thus, the conventional gateway passes telephone traffic from theSCN network to the IP network by using IP telephony signalling used inthe IP based telephony.

[0011] For this, it is necessary to provide the switch devices forspecial interfaces which are adapted to connect the gateways to theswitch device. This results in a complicated handling of the gateways.

[0012] Furthermore, it is necessary to provide the switch devices withspecial control elements related to the gateways, which are different tothe normal exchange terminals. Hence, a complicated hardware structureof the switch devices are necessary.

SUMMARY OF THE INVENTION

[0013] Thus, the object underlying the invention is to eliminate theabove drawbacks and to enable an easy installation of new IP telephonyinterfaces (gateways) between conventional switch devices and an IPnetwork.

[0014] This object is solved by a network control device for controllingdata transfer in a first network, wherein the data transfer is suppliedfrom a second network via a switch device adapted to control the secondnetwork and an interface establishing device connected between theswitch device and the first network, and said network control devicecontrols the interface establishing device by using signallingassociated with the first network.

[0015] Furthermore, the above object is solved by an interfaceestablishing device for providing an interface between a first networkand a second network, wherein the interface establishing device isadapted to receive data from the second network by using signallingassociated with the second network and to transmit the data to the firstnetwork by using signalling associated with the first network.

[0016] Alternatively, the above object is solved by a method forcontrolling a network system comprising a first network, a secondnetwork, an interface establishing device providing interface betweenthe networks, and a switch device to which the interface establishingdevice is connected and which controls the second network, the methodcomprising the steps of controlling the interface establishing devicevia the first network by using signalling associated with the firstnetwork, controlling the switch device via the first network by usingsignalling associated with the second network.

[0017] By the above method, the signalling and data transfer between theswitch device and the gateway is performed in the same way as thesignalling and data transfer between the switch device and a normalexchange terminal.

[0018] Therefore, it is not necessary to provide the switch devices withspecial interfaces which are adapted to connect the gateways to theswitch device. Furthermore, the switch devices do not have to beequipped with special control elements related to the gateways, whichare different to the normal exchange terminals.

[0019] Hence, an easy handling of the gateways is possible. That is,according to the invention a telecom operator is enabled to installeasily new IP telephony interfaces (gateways) between conventionalswitch devices and the IP network. This is valid both for fixed(wireline) networks like the normal public switched telephone network(PSTN) and mobile networks like GSM. The invention can be applied evenfor various access server solutions, which are needed to provide telecomsubscribers with Internet connections.

[0020] Further advantageous developments are defined in the dependentclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be more readily understood withreference to the accompanying drawings in which:

[0022]FIG. 1 shows two different networks connected by a gatewayaccording to the prior art,

[0023]FIG. 2 shows two different networks connected by a gatewayaccording to an embodiment of the invention,

[0024]FIG. 3 shows signalling of a call routed through the networksaccording to the embodiment of the invention, and

[0025]FIG. 4 shows a flowchart illustrating the method according to theembodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] In the following, a preferred embodiment of the invention isdescribed in more detail with reference to the accompanying drawings.

[0027] The invention is based on a separate network element called CallProcessing Server (CPS), which is the same as or a part of a gatekeeper(GK) according to the IP specification H.323. In the following, the CallProcessing Server is referred to as CPS network element. The CPS networkelement is normally handling IP telephony calls by using H.323signalling or other relevant IP signallings like SIP (Session InitiationProtocol). According to this invention, the CPS network element supportseven a common channel signalling (SS7, i.e. signalling system number 7)widely used in telecom networks, as shown in FIG. 2. It is noted that inFIG. 2 the CPS network element is denoted with the reference sign CPS.Furthermore, in the example of FIG. 2 the CPS network element and thegatekeeper are constructed as one unit. Nevertheless, both units can beconstructed as separate units.

[0028]FIG. 2 shows two different networks, an IP based network and acircuit switched network SCN like a public switched telephone network(PSTN) or a GSM network, as FIG. 1.

[0029] These networks are connected by a gateway GW, which is connectedto a switch device SD. The switch device SD is adapted to operate theSCN network. In detail, to the switch device SD an exchange terminal ETfor a trunk line is connected.

[0030] In the following, the installation and use of the gateway (IPgateway unit) GW is described.

[0031] The gateway GW is functioning towards the switch device SD andthe corresponding exchange software included therein like an exchangeterminal ET for a trunk line (e.g., E1/T1, 2 Mbits/s PCM line inEurope). The gateway can be a plug-in-unit in an integrated case. Thus,the installation is easy because in this manner, the gatewayplug-in-unit simply replaces an ET plug-in-unit. Therefore, the gatewaycan also be referred to as an IP exchange terminal (IPET). Nevertheless,it is also possible to provide an external unit with several ET standardinterfaces, to which gateways can be connected.

[0032] The gateway GW includes on the IP network side an IP interface,IP protocols and the logic which provides conversion (DSP digital signalprocessing) between the audio signals carried on telephone circuits anddata packets carried over the IP network.

[0033] The CPS network element controls the gateway GW from the IPnetwork side. This is indicated in FIG. 2 by the control signal CS whichis transmitted from the CPS network element to the gateway GW via the IPnetwork. The CPS network element is capable to control a pluralitygateway units, which might be installed in a plurality of switchdevices.

[0034] The CPS network element controls the gateway GW, as mentionedabove. In detail, the CPS network element loads the software necessaryfor the gateway GW over the IP network. Furthermore, it controls theparameters of the gateway GW. Moreover, it controls the telephonetraffic according to the signalling.

[0035] With respect to the signalling, it is noted that the CPS networkelement includes the signalling software both for IP telephony (H.323,SIP) and SS7 signalling (such as ISUP=ISDN user part) used in telecomnetwork.

[0036] As a call is routed from the switched circuit network SCN (like aPSTN) to the IP network, the switch device SD signals with the CPSnetwork element by using ISUP signalling over the SS7 link just as itnormally does with other telecom switch devices, to which acorresponding call is directed to. The CPS network element routes thecall forward to the IP network by using IP telephony signalling (H.323)with the target and sends the correct target IP address to the gatewayGW which takes care of the call in the “outgoing trunk” of the switchdevice SD. This is shown in FIG. 3 which is described in the following.

[0037]FIG. 3 shows two networks IP and SCN connected via the gateway GW.Same reference characters as in FIG. 2 refer to same elements as shownin FIG. 2, thus, a description of these elements is omitted.

[0038] In the network system shown in FIG. 3, a terminal TE is connectedto the IP network. This terminal can be a computer with a telephoneconnected thereto, for example.

[0039] Furthermore, a call path is illustrated by a dash-dotted line.The origin of the call is located in the SCN network. The call istransmitted via the exchange terminal ET to the switch device SD, fromwhich it is sent to the gateway GW. Then, the call is routed through theIP network from the gateway GW to the terminal TE.

[0040] The dotted lines shown in FIG. 3 indicate the signalling used.From the origin in the SCN network to the switch device, ISUP signalling(over SS7) is used, for example. This call “routing” (call forwarding)in the SCN network is performed in a conventional manner.

[0041] However, the call forwarding from the switch device SD to thegateway GW is also performed by using ISUP signalling. Thus, thefunction of the gateway GW is for the switch device SD the same as thatof the exchange terminal ET.

[0042] As described above, the use of the ISUP signalling is performedunder the control of the CPS network element. For routing the callthrough the IP network, an IP signalling is required. As an example, theH.323 signalling is shown. The routing of the call by using the H.323signalling starts in the gateway GW, such that the gateway GW iscontrolled by the CPS network element by using both the signalling forthe SCN network (i.e., ISUP signalling) and the signalling for the IPnetwork (i.e., H.323 signalling).

[0043] By this measure, the switching device can treat the gateway GW inthe same way as it would treat an exchange terminal in the same place.

[0044] Furthermore, in practice the gateway GW and the exchange terminalET are both constructed as plug-in-units which are inserted in slots.Both of these units can be constructed such that they can be inserted inthe same type of slot, hence, have the same connection inputs andoutputs. Thus, a gateway plug-in-unit can be inserted in the same placewhere an exchange terminal plug-in-unit has been before. This measurealso enables easy installing of the gateways.

[0045] As mentioned above, the invention is based on the separatenetwork element Call Processing Server (CPS), which includes thesignalling software used in both SCN and IP network telephony.Furthermore, the CPS network element controls gateways of conventionalswitch devices. According to the invention, the gateways function liketraditional trunk line interfaces (exchange terminals). Therefore, it isnot necessary to modify an existing conventional switch device. Thus, asoftware upgrade in switch device is not required, for example.Moreover, the software used in the gateways can easily be maintained.

[0046] Furthermore, the IP interface (i.e., the gateway) does not bringany new functions which affect the switch device software. Therefore,the gateways controlled by the CPS network element according to theinvention can easily be installed in existing switch devices.

[0047] Moreover, a network system can easily be updated with the CPSnetwork elements according to the invention, since the gatewaysaccording to the invention can be used while conventional gatekeepersand conventional gateways are still present in the IP network.Therefore, an introduction of the new CPS network elements (i.e., thenetwork control devices) according to the invention can be easily andsmoothly effected.

[0048] Furthermore, all IP related functions of the gateway arecontrolled by the CPS network element from IP network side.

[0049] The calls which are forwarded from an origin in the SCN networkto trunk lines and finally to the IP network via gateways are signalledwith the ISUP signalling between the CPS network element and the switch.

[0050] The CPS network element uses the IP telephony signalling in theIP network (e.g., with H.323 terminal) when calls are forwarded to IPusers and passes the IP address gateway unit.

[0051] Although not described above, a call can also be transmitted fromthe IP network to the SCN network with the same signalling as shown inFIG. 3. That is, the routing directions are working in the same way inboth directions and the call from IP network PSTN is routed in thecorresponding way.

[0052] Moreover, it has to be noted that the networks concerned do nothave to be different from each other. That is, although the connectionof a switched circuit network SCN and a packet switched network (IPnetwork) were shown as examples for the networks, it is also possiblethat both networks are basically of the same type (e.g., packetswitched), and that the only difference between them is the use of adifferent signalling.

[0053] In the following, the method according to the invention isdescribed with respect to the flowchart shown in FIG. 4, in which thebasic idea of the invention is summarized. This method is performed bythe call processing server CPS.

[0054] In step S1, the gateway GW is controlled via the IP network byusing H.323 signalling. This control of the gateway GW is furtherdescribed in steps S2 to S4. That is, in step S2 the parameters of thegateway GW are controlled via the IP network. Then, in step S3 it isdecided whether an update of the gateway GW is required. For example,this can be necessary in case a new gateway GW is connected to theswitch device SD. Then, the software actually needed has to be loadedvia the IP network in step S4. This measure serves to provide a veryeasy installing of new gateways, i.e., IP telephony interfaces by simplyinserting the gateway units in the corresponding slot of the switchdevice SD, for example, and loading the required software via the IPnetwork. Hence, the switch device SD is not required to perform anycontrol associated with the IP telephony. Furthermore, the switch deviceSD is also controlled via the IP network in step S5. It has to be notedthat the control of the switch device only includes the control withrespect to the gateway GW. Furthermore, as mentioned above, this controlis performed by using the ISUP signalling.

[0055] It has to be noted that the signalling used for the SCN networkis not limited to the ISUP signalling, but also other suitablesignalling can be used. Likewise, the signalling for the IP network isnot limited to H.323 signalling, but also other suitable siganlling canbe used.

[0056] Thus, according to the invention a telecom operator is enabled toinstall easily new IP telephony interfaces (gateways) betweenconventional switch devices and the IP network. This is valid both forfixed (wireline) networks like the normal public switched telephonenetwork (PSTN) and for mobile networks like GSM. The invention can beapplied even for various access server solution, which are needed toprovide telecom subscribers with Internet connections.

[0057] The above description and accompanying drawings only illustratethe present invention by way of example. Thus, the embodiments of theinvention may vary within the scope of the attached claims.

1. A network control device (CPS) for controlling data transfer in afirst network (IP), wherein said data transfer is supplied from a secondnetwork (SCN) via a switch device (SD) adapted to control said secondnetwork (SCN) and an interface establishing device (GW) connectedbetween said switch device (SD) and said first network (IP), and saidnetwork control device (CPS) controls said interface establishing device(GW) by using signalling associated with said first network (IP).
 2. Thenetwork control device according to claim 1, wherein said networkcontrol device (CPS) controls a plurality of switch devices (SD) andinterface establishing devices (GW1) via said first network (IP).
 3. Thenetwork control device according to claim 1 or 2, wherein said firstnetwork (IP) is an IP based network and said second network (SCN) is aswitched circuit network.
 4. The network control device according to oneof the previous claims, wherein said network control device (CPS) islocated remotely from said interface establishing device (GW) andcontrols said interface establishing device (GW) by transmitting controlsignals (CS) via said first network (IP).
 5. The network control deviceaccording to one of the previous claims, wherein said network controldevice controls parameters of said interface establishing device (GW).6. The network control device according to one of the previous claims,wherein said network control device loads control software for saidinterface establishing device (GW) via said first network (IP) into saidinterface establishing device (GW).
 7. The network control deviceaccording to one of the previous claims, wherein said data transferrelates to telephone traffic.
 8. An interface establishing device (GW)for providing an interface between a first network (IP) and a secondnetwork (SCN), wherein said interface establishing device (GW) isadapted to receive data from said second network (SCN) by usingsignalling associated with said second network (SCN) and to transmitsaid data to said first network (IP) by using signalling associated withsaid first network (IP).
 9. The interface establishing device accordingto claim 8, wherein said interface establishing device (GW) is adaptedto receive control signals (CS) from a remotely located network controldevice (CPS).
 10. The interface establishing device according to claim 8or 9, wherein said interface establishing device (GW) is connectable toa switch device (SD) adapted for controlling said second network (SCN).11. The interface establishing device according to claim 10, whereinsaid switch device (SD) comprises at least one connecting means forconnecting an exchange terminal (ET) for a trunk line, and saidinterface establishing device (GW) is adapted to be connected to one ofsaid connecting means in place of said exchange terminal (ET).
 12. Theinterface establishing device according to claim 11, wherein saidconnecting means is a slot, and said exchange terminal (ET) and saidinterface establishing device (GW) are constructed as plug-in-units suchthat both said exchange terminal (ET) and said interface establishingmeans (GW) can be inserted in said slot.
 13. A network system comprisinga network control device according to one of the claims 1 to 7 and aninterface establishing device according to one of the claims 8 to 12.14. A method for controlling a network system comprising a first network(IP), a second network (SCN), an interface establishing device (GW)providing interface between said networks, and a switch device (SD) towhich said interface establishing device (GW) is connected and whichcontrols said second network (SCN), said method comprising the steps ofcontrolling (S1, S2, S3, S4) said interface establishing device (GW) viasaid first network (IP) by using signalling associated with said firstnetwork (IP), controlling (S5) said switch device (SD) via said firstnetwork (IP) by using signalling associated with said second network(SCN).
 15. The method according to claim 14, wherein said controllingstep comprises the steps of controlling (S2) parameters of saidinterface establishing device (GW) and loading (S4) control software forsaid interface establishing device (GW) if it is decided that an updateis necessary (S3).